Oestrogen and progesterone receptors in mammary tumours of male SHN mice grafted with pituitaries in comparison with females.

Mammary tumour induced by pituitary grafting in SHN male mice is promising as an animal model for male breast cancer. In this study, these mice (group MC) were found to differ little from the intact female SHN (group FC) in cytosolic oestrogen receptor (OR) level in either normal or neoplastic mammary glands. On the other hand, Progesterone receptor (PR) level in normal glands tended to be lower in group MC than in group FC, which was recovered by chronic treatment with oestradiol benzoate (group OB). Little difference in PR level in mammary tumours was seen between groups MC and FC. Mammary tumorigenesis was significantly inhibited by chronic treatment with dihydrotestosterone to male mice with pituitary grafts (group DHT). This is associated with the significant decline in PR level in normal mammary glands, while not in mammary tumours. There were no significant correlations between OR and PR levels in normal or neoplastic mammary glands, or between normal and neoplastic mammary glands in OR or PR in all groups except group MC, in which the correlation between OR and PR in mammary tumour was significant. All findings indicate that OR and PR states in mammary tumours of male mice induced by pituitary grafting are essentially similar to the spontaneous mammary tumours of females as postulated in the human.